U.S. patent application number 11/304889 was filed with the patent office on 2007-06-21 for geometric configuration and confinement for deflagration to detonation transition enhancement.
This patent application is currently assigned to General Electric Company. Invention is credited to David Michael Chapin, Anthony John Dean, Adam Rasheed, Venkat Eswarlu Tangirala.
Application Number | 20070137172 11/304889 |
Document ID | / |
Family ID | 38171804 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137172 |
Kind Code |
A1 |
Rasheed; Adam ; et
al. |
June 21, 2007 |
Geometric configuration and confinement for deflagration to
detonation transition enhancement
Abstract
A pulse detonation combustor is provided with a fuel-air mixer
located upstream from a detonation chamber. A fuel-air mixture
exits the fuel-air mixer and enters the detonation chamber, where
it is ignited by an ignition source. The flow from the fuel-air
mixer passes over the surface of a center body, which extends
downstream from the fuel-air mixer. The surface of the center body
contains at least one turbulence generator, which imparts
additional turbulence in the fuel-air mixture passing through the
chamber. The turbulence generator aids in the mixing of the fuel
and air of the fuel-air mixture to enhance the deflagration to
detonation transition within the pulse detonation combustor.
Inventors: |
Rasheed; Adam; (Glenville,
NY) ; Dean; Anthony John; (Scotia, NY) ;
Tangirala; Venkat Eswarlu; (Niskayuna, NY) ; Chapin;
David Michael; (Niskayuna, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
|
Family ID: |
38171804 |
Appl. No.: |
11/304889 |
Filed: |
December 16, 2005 |
Current U.S.
Class: |
60/39.76 ;
60/39.821 |
Current CPC
Class: |
F23R 3/16 20130101; F23R
7/00 20130101; F02K 7/02 20130101; F02C 5/00 20130101; Y02T 50/60
20130101; F23R 3/14 20130101 |
Class at
Publication: |
060/039.76 ;
060/039.821 |
International
Class: |
F02C 5/00 20060101
F02C005/00 |
Claims
1. A pulse detonation combustor; comprising: a fuel-air mixer from
which a mixture of fuel and air exits into a detonation chamber; an
ignition source coupled to said chamber to ignite said fuel-air
mixture; and at least one center body extending from said fuel-air
mixer into said chamber, wherein said center body has at least one
turbulence generator on a surface of said center body.
2. The pulse detonation combustor of claim 1, wherein said center
body has a plurality of said turbulence generators on said
surface.
3. The pulse detonation combustor of claim 1, wherein said center
body is positioned coaxially with said mixer.
4. The pulse detonation combustor of claim 1, wherein said
turbulence generator has either a concave or convex shape, with
respect to said surface.
5. The pulse detonation combustor of claim 2, wherein at least some
of said generators have a convex or concave shape with respect to
said surface.
6. The pulse detonation combustor of claim 1, wherein said ignition
source is positioned downstream of said mixer, and adjacent to said
center body.
7. The pulse detonation combustor of claim 1, wherein said ignition
source is located at a distance either 2D downstream from said
mixer, where D is a diameter of said detonation chamber, or
corresponding to a midpoint of said center body along a length of
said center body.
8. The pulse detonation combustor of claim 1, wherein said center
body comprises at least one nozzle through which at least one of
fuel, air and an additional fuel-air mixture passes to enter said
chamber.
9. The pulse detonation combustor of claim 1, wherein said center
body comprises a central portion which has a cross-sectional area
which is larger than a cross-sectional area of both an upstream
portion and a downstream portion.
10. The pulse detonation combustor of claim 1, wherein said center
body comprises a central portion which has a cross-sectional area
which is smaller than a cross-sectional area of both an upstream
portion and a downstream portion.
11. The pulse detonation combustor of claim 2, wherein said
plurality of turbulence generators are divided into a plurality of
groups, where a first group of turbulence generators has at least
one geometric characteristic which is different from the remaining
turbulence generators.
12. The pulse detonation combustor of claim 1, wherein said
ignition source is coupled to said center body.
13. The pulse detonation combustor of claim 1, further comprising
at least one additional ignition source.
14. The pulse detonation combustor of claim 13, wherein at least
one of said ignition source and said at least one additional
ignition source is coupled to said center body.
15. The pulse detonation combustor of claim 1, further comprising a
plurality of center bodies extending from said fuel air mixer.
16. The pulse detonation combustor of claim 15, wherein said
plurality of pulse detonation are positioned symmetrically with
respect to said fuel air mixer.
17. The pulse detonation combustor of claim 1, wherein the center
body extends the entire length of said chamber, and said at least
one turbulence generator is positioned on an upstream section of
said center body.
18. The pulse detonation combustor of claim 1, wherein said center
body comprises a central portion which has a cross-sectional area
which is larger than a cross-sectional area of at least one of an
upstream portion and a downstream portion.
19. The pulse detonation combustor of claim 1, wherein said center
body comprises a central portion which has a cross-sectional area
which is smaller than a cross-sectional area of at least one of an
upstream portion and a downstream portion.
20. A pulse detonation combustor; comprising: a fuel-air mixer from
which a mixture of fuel and air exits into a detonation chamber; an
ignition source coupled to said chamber to ignite said fuel-air
mixture; and at least one center body extending along a length of
said chamber downstream of said fuel-air mixer into said chamber,
wherein said center body has at least one turbulence generator on a
surface of said center body.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an apparatus and method for
enhancing mixing of a fuel-air mixture in a pulse detonation
combustor to reduce the overall run-up time and/or distance to
detonation of the mixture.
[0002] In pulse detonation combustors, a mixture of fuel and air is
ignited and is transitioned from deflagration to detonation, so as
to produce supersonic shock waves, which can be used to provide
thrust, among other functions. This deflagration to detonation
transition (DDT) typically occurs in a smooth walled tube or pipe
structure, having an open end through which the exhaust exits.
[0003] The deflagration to detonation process begins when a
fuel-air mixture in a tube is ignited via a spark or other source.
The subsonic flame generated from the spark accelerates as it
travels along the length of the tube due to various chemical and
flow mechanics. As the flame reaches sonic velocity, shocks are
formed which reflect and focus creating "hot spots" and localized
explosions, eventually transitioning the flame to a super sonic
detonation wave.
[0004] As indicated previously, the above described process takes
place along the length of a tube, and is often referred to as the
run-up to detonation., i.e. the distance/time from spark to
detonation.
[0005] However, a problem with existing smooth walled tube
structures is the relative long run-up length necessary to achieve
detonation of the fuel-air mixture. In fact, in many applications
the run-up length, up to detonation, can be such that the ratio L/D
(i.e. tube length over tube diameter) is greater than 100. This
run-up length is problematic when trying to incorporate the pulse
detonation combustor in applications where space and weight are
important factors, such as aircraft engines.
[0006] Efforts have been made to reduce the run-up length to
detonation by using obstacles within the flow, in an effort to
enhance mixing of the fuel-air mixture. However, there still exists
a need to reduce the run-up length and accelerate the development
of the flame kernel around the spark or ignition source.
SUMMARY OF THE INVENTION
[0007] In an embodiment of the present invention, a turbulence
generator is positioned upstream of the spark region to aid in the
mixing of the fuel-air mixture and a shaped center body is
positioned within the tube to further enhance mixing and accelerate
the stretching of the flame, so as to reduce the run-up length to
detonation. Specifically, the present invention employs at least
one fuel-air mixer located upstream of the ignition source which
imparts turbulence into the mixture, which enhances mixing.
Further, at least one shaped center body is placed within the flow
path of the fuel-air mixture to further enhance the mixing. The
shaped center body is configured such that it imparts additional
turbulence into the flow.
[0008] In an embodiment of the present invention, the shaped
center-body contains a number of recessions, dimples or protrusions
which further interact with the flow, thus imparting additional
turbulence in the flow, thus reducing the overall run-up
length.
[0009] By adjusting various parameters, such as the shape, size,
and surface contour of the center body, the positioning and shape
of the fuel-air mixer, and the positioning of the spark or ignition
source, the present invention reduces the DDT run-up length and
run-up time in a pulse detonation combustor, allowing for the
construction of more compact and practical PDC.
[0010] As used herein, a "pulse detonation combustor" ("PDC") is
understood to mean any combustion device or system where a series
of repeating detonations or quasi-detonations within the combustor
cause a pressure rise and subsequent acceleration of the combustion
products as compared to the pre-burned reactants. A
"quasi-detonation" is a combustion process that produces a pressure
rise and velocity increase higher than the pressure rise produced
by a deflagration wave. Typical embodiments of PDCs include a means
of igniting a fuel/oxidizer mixture, for example a fuel/air
mixture, and a confining chamber, in which pressure wave fronts
initiated by the ignition process coalesce to produce a detonation
wave. Each detonation or quasi-detonation is initiated either by
external ignition, such as spark discharge, laser pulse, or plasma
pulse or by gas dynamic processes, such as shock focusing,
autoignition or by another detonation via cross-firing. The
geometry of the detonation chamber is such that the pressure rise
of the detonation wave expels combustion products out the PDC
exhaust to produce a high-velocity or supersonic jet stream. As
known to those skilled in the art, pulse detonation may be
accomplished in a number of types of detonation chambers, including
detonation tubes, shock tubes, resonating detonation cavities and
annular detonation chambers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The advantages, nature and various additional features of
the invention will appear more fully upon consideration of the
illustrative embodiment of the invention which is schematically set
forth in the figures, in which:
[0012] FIG. 1 is a diagrammatical representation of a pulse
detonation combustor according to an embodiment of the present
invention;
[0013] FIG. 2 is a diagrammatical representation of a pulse
detonation combustor according to another embodiment of the present
invention;
[0014] FIG. 3 is a diagrammatical representation of a pulse
detonation combustor according to an alternative embodiment of the
present invention;
[0015] FIG. 4 is a diagrammatical representation of an aft portion
of a pulse detonation combustor according to a further embodiment
of the present invention;
[0016] FIG. 5 is a diagrammatical representation of an aft portion
of a pulse detonation combustor according to a further alternative
embodiment of the present invention;
[0017] FIG. 6 is a diagrammatical representation of a pulse
detonation combustor according to another alternative embodiment of
the present invention; and
[0018] FIG. 7 is a diagrammatical representation of a pulse
detonation combustor according to an additional alternative
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention will be explained in further detail by
making reference to the accompanying drawings, which do not limit
the scope of the invention in any way.
[0020] FIGS. 1 through 6 depict a cross-sectional side view of a
pulse detonation combustor 100 according to various embodiments of
the present invention. The pulse detonation combustors 100 contain
a forward flow section 14 positioned upstream of a fuel-air mixer
16, which is, in turn, positioned upstream of an ignition source
10, a detonation chamber 12, and a center body 18 (FIG. 1). Each of
the FIGS. 1 through 6 depict an alternative embodiment of the
present invention, in which the center body is show with various
alternative configurations.
[0021] Turning now to FIG. 1, an exemplary embodiment of the
present invention is shown. In this embodiment, the pulse
detonation combustor 100 contains a forward flow section 14
positioned upstream of a fuel-air mixer 16, which is, in turn,
positioned upstream of an ignition source 10, a detonation chamber
12, and a center body 18. Air flow is passed through the forward
flow section 14 into the fuel-air mixer 16, in which fuel is mixed
with the air flow. After mixing, the fuel-air mixture passes into
the detonation chamber 12, where it is ignited by the ignition
source 10.
[0022] In an embodiment of the present invention, the fuel-air
mixer 16 is configured with turbulence generators, swirl vanes, or
similar structure (not shown) which adds to the turbulent nature of
the mixture exiting the mixer 16, to further enhance the mixing of
the fuel-air mixture. It is noted that the specific configuration
and structure of the turbulence generators in the mixer 16 are to
be configured so as to optimize the mixing of the fuel-air mixture
as it enters the chamber 12.
[0023] In an additional embodiment, the flow from the forward flow
section 14 can already be a mixture of fuel and air. In this
embodiment, additional fuel may be added in the mixer 16, or the
mixer 16 may simply act to further mix the fuel air mixture from
the forward section 14 and not add additional fuel.
[0024] Extending from a central portion of mixer 16 is a shaped
center body 18. As shown the center body 18 extends from the mixer
16 to a point past the ignition source 10. The overall length and
diameter of the center body 18 is determined based on operational
parameters and characteristics, to optimize performance. In one
embodiment of the present invention, the overall cross-sectional
shape of the center body 18 is circular, as shown in FIG. 1.
However, the present invention is not limited to this, as the
cross-sectional shape can be additional shapes, such as octahedral,
polygonal, etc. The overall shape of the center body 18 is
determined to optimize performance and minimize DDT run-up.
[0025] The location of the ignition source 10 along the length of
the center body 18 is optimized so as to provide the shortest
run-up distance and most efficient operation of the combustor 100.
In one embodiment of the present invention, the ignition source 10
is positioned 2D downstream of the aft face of the mixer 16, where
"D" is the inner diameter of the detonation chamber 12. In another
embodiment, the ignition source 10 is positioned at the mid-point
along the length of the center body 18. Although only one ignition
source 10 is shown in the FIG. 1 embodiment, the present invention
is not limited to this, and in alternative embodiments more than
one ignition sources may be used.
[0026] As shown in FIG. 1, and the remaining figures, the ignition
source 10 is shown coupled to the wall of the chamber 12. However,
in an alternative embodiment the ignition source 10 is coupled to
the center body 18. In a further embodiment, at least one ignition
source is coupled to the wall of the chamber 12, and at least one
other ignition source 10 is coupled to the center body 18.
[0027] As shown in FIG. 1, positioned along a length of center body
18 are a plurality of turbulence generators 20. These generators 20
create further turbulence and mixing of the fuel-air mixture as it
passes along the chamber 12. As discussed above, this further
mixing aids in accelerating the flame during deflagration, in order
to more quickly achieve detonations. The shorter run-up
distance/time allows for the pulse detonation combustor 100 to be
made shorter, and also allow for higher operational frequencies of
the combustor 100.
[0028] Positioned at the end of the center body 18 is an end
portion 22. The end portion 22 is shaped so as to prevent flame
holding within the chamber. The shape of the end portion 22 is to
be optimized so as to prevent flame holding and permit the optimal
performance of the device. In another embodiment, the end portion
22 is not used, or the shape may be changed as required to achieve
the desired operational characteristics.
[0029] As shown in FIG. 1, the generators 20 are concave dimple
structures in the surface of the center body 18. These dimples
provide a similar effect to dimples used on a golf ball, where the
dimples create a turbulent flow over the surface of the center body
18. As shown, the dimples are spherical in shape. However, the
present invention is not limited to this configuration. Namely, the
specific shape, depth, diameter, number and geometric configuration
of the generators 20 are to be optimized so as to impart the
maximum amount of mixing without inhibiting or otherwise adversely
affecting the downstream flow of the fuel-air mixture or DDT.
[0030] In a further embodiment, the generators 20 are not concave
(i.e. recessed with respect to the outer surface of the center body
18), but are convex and thus extending into the flow of the
fuel-air mixture. Again, the geometric characteristics of the
generators 20 are selected to optimize performance.
[0031] In the embodiment shown in FIG. 1, the generators 20 are
distributed symmetrically along the length and around the center
body 18. However, the present invention is not limited to this
configuration as the generators 20 may be distributed asymmetrical
to optimize performance due to the interaction with the ignition
source 10. Further, in an additional embodiment, the generators 20
are divided into a number of different types of generators which
have different geometric properties. Thus, the center body 18 may
contain two different types of generators, where the first type of
generator 20 has at least one physical property (i.e. depth, shape,
diameter, height, etc.) which is different from a second type of
generators 20. For example, a center body 18 may contain three
different types of turbulence generators 20, where the first type
has a first diameter and depth, the second type has a second
diameter and depth, and the third type has a third diameter and
depth. Such a configuration may be used to accelerate the mixture
in one area of the chamber faster than another portion.
[0032] In a further embodiment, the center body 18 is configured
with a manifold type structure within the center body 18 to permit
the circulation of air/liquid/fuel to allow for cooling of the
center-body 18.
[0033] In an additional embodiment, the center body 18 is further
equipped with a plurality of nozzles 28 which inject additional
fuel, air and/or a fuel-air mixture into the chamber 12 to further
enhance the performance of the combustor 100, or the DDT process.
In an alternative embodiment, the nozzles are used to inject air
into the chamber during a purge phase of operation. This air
assists in purging the chamber 12 between detonations.
Additionally, the air can be injected at a temperature to provide a
cooling effect to the surfaces of the chamber 12, ignition source
10 and center body 18. In one embodiment, a nozzle is positioned at
the end of the end portion 22 to inject air to aid in the purge
process.
[0034] In another embodiment, fuel is injected through the nozzles
28 into the chamber, such that the fuel acts as a coolant to the
center body 18, allowing heat to transfer from the center body to
the fuel, thus also pre-heating the fuel prior to it entering the
chamber. In this embodiment, the fuel is pre-heated as heat is
transferred from the center body 18 (i.e. as the center body 18 is
cooled.)
[0035] FIG. 2 depicts a further embodiment of the present
invention, where the generators 26 on the center body 24 are larger
than those shown in FIG. 1. As indicated above, the specific shape,
depth, diameter, number and geometric configuration of the
generators 26 are to be optimized so as to impart the maximum
amount of mixing without inhibiting or otherwise adversely
affecting the downstream flow of the fuel-air mixture or DDT.
[0036] FIG. 3 shows another embodiment of the present invention,
where the overall cross-section of the center body 30 varies along
the length of the center body 30. In this embodiment, a central
region 34 of the center body 30 has a larger cross-sectional area
than both an upstream 36 and downstream 38 portion of the center
body 30. Further, as shown in this embodiment, the center body
contains a number of turbulence generators 32. By varying the
diameter along the length of the center body 18 the local bulk
velocity of the mixture and flow can be tailored to optimize DDT.
Thus, the specific cross-sectional size and shape of the center
body may be varied by a skilled artisan to achieve the desired
performance and operational characteristics.
[0037] The embodiment shown in FIG. 4 is similar to that shown in
FIG. 3. However, in the FIG. 4 embodiment the generators 44 on the
center body 40 are convex. In a further embodiment (not shown), the
center body 40 contains a plurality of both convex and concave
shaped generators 44. The number, shape and distribution of each of
the convex and concave generators are made to maximize mixing of
the fuel-air mixture and to minimize the DDT run-up.
[0038] FIG. 5 depicts a further alternative of the present
invention, where the center body 50 has a center portion 52 which
is smaller in cross-section than upstream and downstream sections.
Further, although this embodiment is shown with the center body 50
having no additional turbulence generators (as in FIGS. 1-4), in an
additional embodiment, additional turbulence generators can be
placed on the surface of the center body 50.
[0039] FIG. 6 shows yet another embodiment of the present
invention, where a central region of the center body contains an
obstacle portion 62 to promote turbulent mixing of the fuel-air
mixture. As shown, the obstacle portion 62 has a cross-section, or
size, which is larger than the remaining portions of the center
body 60. This configuration allows the obstacle 62 to interfere
with the flow, thus creating turbulence. The present invention is
not limited to the embodiment shown in FIG. 6. For example, it is
contemplated that the central portion of the center body 60
contains only a recessed portion 64, and no obstacle portion 62. As
with the embodiments discussed above, the exact geometric
configuration of the obstacle 62 and recessed portion 64 are
optimized to maximize mixing and minimize flame holding. In a
further embodiment, the obstacle portion 62 is positioned upstream
of the ignition source.
[0040] In each of FIGS. 1 through 6, a single center body is shown
coupled co-axially with the mixer 16 of the pulse detonation
combustor 100. However, the present invention is not limited to
this embodiment. Specifically, an alternative embodiment may
contain a plurality of center bodies extending downstream from the
mixer 16, where the center bodies are positioned symmetrically and
radially with respect to a centerline of the mixer. For example, an
embodiment may contain three center bodies which are centered in a
triangular configuration with respect to the exit face of the mixer
16.
[0041] Further, in each of the FIGS. 1 through 6, the center body
18 is shown to be shorter in length than the chamber 12. However,
in an alternative embodiment, the center body 18 may extend the
entire length of the chamber 12, or beyond. An embodiment of this
aspect of the present invention is shown in FIG. 7. In this
embodiment, the upstream most portion 72 of the center body 18 is
used as described above, to enhance mixing. A central portion 74 is
shaped and configured to optimize shock reflections, from the
detonation process, and focus the shock reflections to enhance hot
spot formation within the detonation. The downstream portion 76 is
configured to facilitate detonation propagation along the length of
the chamber 12. The physical characteristics of the central and
downstream portions are determined to optimize the desired
performance characteristics. Furthermore, as the cross-sectional
area of the detonation chamber decreases due to the presence of the
center body, the bulk velocity of the flow during the fuel fill and
the purge processes of the PDC cycle increases, thereby decreasing
the fuel fill time and the purge time. As the cycle time decreases
(due to decreasing fill time and purge time), the frequency of the
PDC cycle operation increases, which in turn increases the
performance of the PDC. In an additional embodiment, the use of
nozzles 28 along a longer length than just the upstream portion 72
would allow for shorter fill times for the chamber 12.
[0042] Although the above discussion has been primarily directed to
the use of the present invention in conjunction with aircraft
engines, those of ordinary skill in the art will recognize that the
present invention may be used with any device using pulse
detonation combustors, where it is desirable to reduce the size of
the pulse detonation combustor. The present invention may also be
used with other components and geometries which are used to further
enhance DDT. For example, the present invention may be coupled with
swirlers, obstacles, etc., which may extend from the chamber walls
or from the mixer, while still maintaining the scope and spirit of
the invention.
[0043] Further, while the invention has been described in terms of
various specific embodiments, those skilled in the art will
recognize that the invention can be practiced with modification
within the spirit and scope of the claims.
* * * * *